You pull out the goat mask and grin. It is stylized, more a humanoid face with goaty features - what you might expect from a faun or satyr. You remember wearing this when you were in Junior High, with some fake fur pants and plastic hooves to be Pan, the goat-god of Greek mythology. The pants and hooves are also in the chest, but too small for you now.
You pull the mask on, a little surprised that it still fits pretty well. The strap is broken, so you have to hold it in place. The rubber is still pliable, and molds to your face. Then you jerk as a mild shock ripples from your head down to your toes. You jerk your hand away, but the mask stays in place. When you reach up to remove it, your fingers touch skin. But not quite the skin you should be feeling. You try to find the edges of the mask, but only feel hair and flesh. Startled, you turn to look in the old floor mirror in the corner. The dusty reflection shows a couple of surprises.
First of all, you are naked. Your clothes have vanished! You look trim and fit, at least, somehow appearing smaller. Second, your face is that of the goat mask, but real. Reaching up, you find the curling horns are now part of your skull, and the protruding muzzle and wide-set eyes are your flesh and bone. As you stare, your eyes turn gold-yellow and the irises become horizontal. Goat's eyes!